We should use UserID object to identify users instead of username.

chrome/browser/ui/ash/user_accounts_delegate_chromeos.cc

Index: chrome/browser/ui/ash/user_accounts_delegate_chromeos.cc
diff --git a/chrome/browser/ui/ash/user_accounts_delegate_chromeos.cc b/chrome/browser/ui/ash/user_accounts_delegate_chromeos.cc
index df024639cf14e9d6ecf68bd63d365057cdbdbbe3..65821195e1a8c4a4138d4d4ebb2d888430fc4c92 100644
--- a/chrome/browser/ui/ash/user_accounts_delegate_chromeos.cc
+++ b/chrome/browser/ui/ash/user_accounts_delegate_chromeos.cc
@@ -16,6 +16,7 @@
 #include "components/signin/core/browser/profile_oauth2_token_service.h"
 #include "components/signin/core/browser/signin_manager.h"
 #include "components/user_manager/user.h"
+#include "components/user_manager/user_id.h"
 #include "google_apis/gaia/gaia_auth_util.h"
 
 namespace chromeos {
@@ -56,7 +57,7 @@ std::string UserAccountsDelegateChromeOS::GetAccountDisplayName(
     const std::string& account_id) {
   const user_manager::User* user =
       ProfileHelper::Get()->GetUserByProfile(user_profile_);
-  if (gaia::AreEmailsSame(user->email(), account_id) &&
+  if (gaia::AreEmailsSame(user->GetUserID().GetUserEmail(), account_id) &&
       !user->display_email().empty())
     return user->display_email();
   return account_id;